In recent times, equipment for testing breath alcohol concentration has become quite common even for personal use. There are a number of consumer or personal breath alcohol testers on the market. These hand-held devices are generally less expensive than the devices used by law enforcement.
Many handheld breath analyzers sold to consumers use a silicon oxide sensor (also called a semiconductor sensor) to determine the blood alcohol concentration. These sensors are prone to contamination and interference from substances other than breath alcohol and therefore require recalibration or replacement every six months. Higher end personal breath analyzers and professional-use breath alcohol testers commonly use platinum fuel cell sensors. These too require recalibration but at less frequent intervals than semiconductor devices, usually once a year.
Calibration is the process of checking and adjusting the internal settings of a breath analyser by comparing and adjusting its test results to a known alcohol concentration. Law enforcement breath analyzers are meticulously maintained and re-calibrated frequently to ensure accuracy.
There are two methods of calibrating a precision fuel cell breath analyzer, the wet bath and the dry gas method. Each method requires specialized equipment and factory trained technicians. It is not a procedure that can be conducted by untrained users or without the proper equipment.
The dry gas method utilizes a calibration standard which is a pre-certified solution containing a precise mixture of alcohol and inert nitrogen available in a pressurised container. The equipment may be portable allowing calibrations to be done when and where required.
The wet bath method utilizes an alcohol/water standard which is a pre-certified solution containing a precise specific alcohol concentration, contained and delivered in specialised breath alcohol simulator equipment. Wet bath apparatus has a higher initial cost than the dry gas method and is not intended to be portable. The standard must be fresh and replaced regularly.
These known methods often limit the end-user from calibrating and checking their own devices due to the high cost and complexity of obtaining certification themselves to produce the required equipment, or to purchase the required equipment from a certified supplier.
U.S. Pat. No. 3,854,319 discloses an alcoholic breath simulator wherein a sample may be simulated by blowing non-alcoholic breath through an elongated enclosure maintained at a given temperature and containing alcohol vapor continuously generated from an absorbent material impregnated with an alcohol-water solution. The breath produced at the enclosure's outlet will constitute a simulated breath sample having a known alcohol concentration. Drawbacks with this device are that the enclosure must be manually perforated and that it requires a non-alcoholic breath in order to give a correct calibration. Furthermore, the breath blown through the device might give rise to errors if not performed correctly, i.e. varying flow rate, insufficient volume etc.
WO 2009/111484 discloses calibration and accuracy check systems for a chemical sniffer, such as a breath alcohol tester, which utilize the dispensing of droplets with determinable concentration of alcohol and/or other liquids in a determinable number either directly to a reaction chamber, or into a carrier gas which can be sampled.
These known devices are still overly cumbersome and complex in use and do not achieve the desired simplicity and accuracy of calibration.
Therefore, there is a need to develop equipment which may be supplied to customers owning breath alcohol testing devices, such that they can perform calibration and testing using simple, inexpensive and disposable devices and methods.